— Drugs used to ease the pain of childbirth could interfere with breastfeeding, a new study suggests.

Siranda Torvaldsen of the University of Sydney, Australia, found that 416 women who received the opioid drug fentanyl by epidural injection during delivery were twice as likely to have stopped breastfeeding by the time their baby was six months old compared with 312 women who did not receive the drug.

Torvaldsen does not know whether this is because the drug has a direct effect on babies ability to suckle or that women who opt for (or need) epidural painkillers are also more likely to stop breastfeeding sooner.

A previous study found that the babies of women who have fentanyl tend to be drowsier at one-day-old, raising the possibility that the drug affects suckling at the critical time when breastfeeding gets established.

"Adverse reaction"

In Australia and the US only around 40% of babies are still receiving at least some breast milk at six months, although the World Health Organization recommends breast feeding exclusively until that age.

Now were aware that painkillers may affect breastfeeding, we need to be sure that women who take them get adequate help, says Torvaldsen.

Sue Jordan of Swansea University, UK, who is an expert on the effects of labour drugs and mental health, says the effect of opioids and epidurals on breastfeeding should be seen as an "adverse drug reaction".

In an article accompanying Torvaldsens study in International Breastfeeding Journal, Jordan calls for extra support for the most vulnerable women "to ensure that their infants are not disadvantaged by this hidden, but far-reaching, adverse drug reaction".